1. Field of the Invention
This invention relates to computer systems and, more particularly, to methods and apparatus for combining digital streams of video and graphics for presentation on an output display.
2. History of the Prior Art
There have been various attempts to combine video data (data used to display television) and graphics data (data used to provide a computer display) for presentation on an output display. Most of these attempts have been directed to providing television programs in a window on a computer screen.
Only a few attempts have been made to provide computer graphics output on a television output display. Because the format of the two sources is so different, it has been the practice to import the video signals into computer memory, change the various signals to the format utilized on the chosen output display, combine the signals, and transfer the data to the output display. In general, this has slowed the presentation of all data on the output display because of the large amount of bus time occupied by the video data.
Moreover, all prior art attempts to combine these two types of data have dealt with analog data presented on an analog output display. At present, digital displays appear to be the choice for the future of both television and computers.
It is desirable to provide a new method and apparatus for combining video and computer graphics data capable of utilizing the most accurate timing signals available to produce displays which accurately present and are capable of differentiating each of the individual streams for presentation on either an analog or a digital output display.
It is, therefore, an object of the present invention to provide a new system for combining video data and computer graphics data to provide an output display more rapidly and accurately than has been previously possible.
This and other objects of the present invention are realized by a single chip system including a first input channel for receiving digital video input data, a second channel for receiving computer graphics data, means for synchronizing the two channels to one another utilizing timing signals which may be selected to provide the most accurate timing available, means for changing the rate of presentation of the computer graphics signals to match the rate of presentation of the video signals, means for adjusting the format in which the computer graphics signals are presented to the same format as the format in which the video signals are presented, and means for selectively blending the computer graphics and video signals furnished as video input data without modification for presentation on a single output display.
This and other objects and features of the invention will be better understood by reference to the detailed description which follows taken together with the drawings in which like elements are referred to by like designations throughout the several views.